Burner



Dec. 22, 1959 R. M. scHlRMER 2,918,118

BURNER Filed Aug. 30, 1954 5 Sheets-Sheet 1 'AT -roR NEYs .N @FmINVENTOR R.M.SCH\RMER www i LA,

AMY-T la Dec. 22, E959 R. M. scHxRMl-:R 2,918,118

BURNER Filed Aug 50, 1954 3 Sheets-Sheet 2 L se.

ATTORNEYS Dec. 22, 1959 R. M. scHlRMER 2,91818 BURNER @ned Aug. 50. 1954s sheets-sheet s INVENTOR. `R. M. SCHIRMER BY MWL W7 AT TOR N EYS mm mmUnited States Patent" BURNER Robert M. Schirmer, Bartlesvilie, Okla.,assignor to Phil- Eips Petroleum Company, a corporation of DelawareApplication August 30, 1954, Serial No. 452,803

4 Claims. (Cl. 153-4) This invention relates to improved burners. In oneof its more specific aspects, this invention relates to combustionapparatus. In another of its more specific aspects, it relates tocontinuous flow combustion apparatus of low pressure drop, highcombustion efliciency and high heat release. In another of its morespecific aspects, this invention relates to an improved apparatus forproducing continuous flow combustion at a high rate of heat release. Inanother of its more specific aspects, it relates to an improved burnerfor jet engines.

In the usual design of combustion apparatus in which a flame isinitiated in a stream of high velocity air, some mechanism must beprovided to decelerate at least a portion of the stream of air beloweffective llame velocity in the combustible mixture to pilot andmaintain the flame seated in the apparatus. Addition of fuel is madeeither directly to the high velocity stream of air upstream of thedeceleration device or in the region of a quiescent zone downstream fromthe deceleration device. In the usual turbo-jet engine, combustion ismaintained in the flame tube or liner, which completely surrounds theflame, and apertures in the liner serve for the addition of such air forthe formation of a near stoichiometric mixture of fuel and air in theprimary combustion zone. The loss of pressure in an apparatus of thistype is considerable. In the usual ram jet engine, a restrictiveelement, usually called a llame holder, is mounted in a stream of highvelocity air and combustion is carried on in the quiescent zonedownstream from this restriction. In the ram jet apparatus, themagnitude of the pressure drop is less than that encountered in theturbojet engine.

In the combustion apparatus commonly employed in gas turbine powerplants, it is necessary to achieve stable and eiiicient combustion offuel and air at high rates of heat release in a relatively confinedspace through which a stream of air is mo-ved at high velocity. It isdesirable in such a combustion system that the pressure loss be low,that the temperature distribution of the cross-section of flow beuniform and that stable combustion be obtained over a wide range offuel-air ratios and severity of inlet conditions. In my copendingapplication Serial No. 346,304, filed April 2, 1953, now abandoned, Ihave described and claimed a combustion apparatus which permits a highrate of heat release to be obtained while maintaining high combustioneiciency and combustion stability.

The following objects will be attained by at least one of the aspects ofthis invention.

It is an object of this invention to provide an improved burner. Anotherobject is to provide an improved apparatus for producing continuous flowcombustion at a high rate of heat release. Another object is to providean apparatus of low pressure drop in which improved combustionefficiency and stability are obtained. Another object of the inventionis to provide a continuous llow combustion apparatus wherein the fuel isdelivered uniformly onto the entire inner surface of the primary com-Mig Patented Dec. 22, 1959 bustion chamber. Another object is to providean irnproved continuous flow combustion apparatus wherein the fuel iscontacted with a catalytic material immediately prior to itsintroduction into the combustion chamber. Other and further objects andadvantages of this invention will be apparent to thoseskilled in the artupon study of the accompanying disclosure and drawing.

I have now developed a combustion apparatus which provides improvedcombustion eiciency and stability compared to conventional apparatuswith comparable pressure drops. Broadly speaking, my combustionapparatus permits the introduction of fuel uniformly onto the entireinner surface of the primary combustion chamber through a porous linerspaced from the inner wall of the chamber, and the introduction of airin the form of a vortex into the primary combustion chamber so that theflow of air spirals or swirls coaxially through the primary combustionchamber. Combustion apparently is effected at the highly turbulent shearinterface of the fuel and the air. The shear interface, and thereforethe combustion occurs near the surface of the porous wall and in themixing zone. Using the combustion apparatus of my invention it ispossible to obtain heat release in the order of 40 millionB.t.u./hr./cu. ft./ atmosphere at overall flow velocities up to 250 ft.per second. Thus the amount of heat release that can be obtained with myimproved combustion apparatus is approximately l0 fold that ofconventional burners now in common usage.

The operation of a jet engine, such as those employed in aircraft, isdependent upon the utilization of the thermal energy released in theengine burner. The combustion of fuel andl airin the burner gives themolecules of the gases high kinetic energy. These gases are ejected fromthe combustion chamber at a high velocity, resulting from the highkinetic energy provided by the thermal energy, and thrust is therebyapplied to the aircraft. Thus the efficiency of a jet engine is afunction of its ability to obtain high heat release under all operatingconditions. The improved burner of my invention has particularapplication in operations where high heat release is required, such asin gas turbines, ram jets, furnaces, and the like.

In my combustion apparatus, all of the air may be used as primary air,or part of the air may be used for secondary air, depending upon theneed and adaptation of the burner. Primary air is admitted through aplurality of tangential openings into the flame tube. Preferably, theseopenings are tangential to the llame tube and are located around theperiphery of the ame tube or around the periphery of a smaller diametermember of the burner located immediately upstream from the llame tube.The air can also be admitted coaxially to the flame tube through swirlvanes so as to produce a vortex of air spiraling coaxially through theame tube. This apparatus for the introduction of air provides a swirlingand spiraling ow of air along the axis of the burner and provides forthe supply of the right amount of air to the fuel over a considerableoperating range of conditions so as to maintain a proper, non-carbonforming residence time.

The .llame tube disposed coaxially within the burner shell isconstructed of an impervious outer tube and a porous inner tube locatedcoaxially within the outer tube and spaced from the outer tube so as toprovide an annular chamber between the two tubes. The annular space issealed at both ends so as to provide a chamber having a porous innerwall.

can flow relatively freely into the combustion zone.

The introduction of the fuel through the structure of the primarycombustion chamber wall provides for the increased rate of heat releaseand for the improved cornbustion stability obtained by the apparatus ofmy in-l vention. The use of a liquid fuel in this combustion apparatusprovides for self-regulation of the wall temperature of the fiame tubein accordance with the latent heat absorbed in the vaporization processoccurring on the inner surface of the primary combustion chamber. Also,the circulation of the fuel in the annular chamber surrounding thecombustion zone and the passage of the fuel through the heated, porousstructure of the inner tube preheats the fuel to improve thereby thecombustion process.

It is a particular feature of this invention that the porous inner tubeof the primary combustion zone can be constructed of a material whichwill catalyze such reactions as cracking and oxidizing so that the fuelemerging into the combustion Zone contains a large proportion ofconstituents having improved combustion and stability characteristics.Thus, a fuel which has been precracked contains acetylene having highburning velocity and a fuel with which supplemental oxygen has beenadmixed before passage through the porous inner tube will containaldehydes, peroxides, and other oxygenated cornpounds.

The porous inner tube used in the combustion apparatus of my inventionis constructed with continuous filamentary ducts through which thecombustible material The material from which the porous tube isconstructed must have high mechanical strength and resistance toelevated temperatures. The tube can be made of various metals or ceramicmaterials such as zirconium oxide, aluminum oxide or silica-alumina. Aconvenient method for constructing a metal porous tube comprisescompressing finely divided metal fragments or lmetal powders andthereafter sinter'ing or partially melting the metal fragments causingthem to adhere to each other and thus to form a porous structure. Boththe primary combustion chamber and the secondary combustion chamber canbe constructed with the porous inner tube or liner, however, thecombustion chamber is preferably constructed with the porous tubelocated in only the primary combustion chamber.

In the drawing: Figure l is a sectional elevation of the improved corn-`bustion apparatus of this invention;

Figure 2 is a cross-section taken along line 2-2 of Figure 1;

Figure 3 is a lsection view showing a modification of the apparatus ofFigure 1;

Figure 4 is a cross-section taken along the line 4-4 of Figure 3;

Figure 5 is a section view showing another modification of the apparatusof Figure l; and

Figure 6 is a cross-section taken along the line 6-6 of Figure 5.

Referringnow to the drawing and particularly to Figure 1, combustionapparatus 10 comprises an outer shell 11 having a flame tube 12coaxially disposed therein. The upstream end of fiame tube 12 ispositioned within support member 13 which is attached to closure member14. The porous ,inner tube 15, of slightly smaller diameter than theinner diameter of flame tube 12, is coaxially disposed within fiame tube12 and extends from the inner surface of support member 13 to a pointdownstream in flame tube 12 where primary combustion ceases. Fuel inletconduit means 16 extends through closure member 14 and support member 13to the annular space 17 in support member 13 coinciding with annularpassage 18 formed by the flame tube 12 and porous tube 15. Closure ring19 located at the downstream end of porous liner seals annular chamber18 at its downstream end.

Afrom the primary combustion zone.

Air inlet 20 extends through shell 11 into the annular space formedbetween shell 11 and ame tube 12. Air inlet 20 can extend eitherradially or tangentially through shell 11. A plurality of primary airinlet conduits 21 extends tangentially from the annular space formedbetween shell 11 and ame tube 12 into cylindrical chamber 22 which ispositioned in support member 13 and which is of a diameter slightlysmaller than the diameter of porous tube 15. A portion of the airintroduced through line 20 is diverted as secondary air and isintroduced into the interior of flame tube 12 downstream from theprimary combustion zone through secondary inlet conduits 23. Conduit 20,when positioned so as to introduce air tangentially into the annularspace formed between shell 11 and flame tube 12, aids in producing thedesired vortex in the primary combustion zone.

Fuel conduit 24 extending through closure member 14 and support member13 supplies fuel for ignition purposes to cylindrical chamber 25 locatedin support member 14. Spark type ignition device 26 extends throughclosure member 14 into chamber 25 for effecting ignition of a pilotfuel, such as propane.

In the operation of the device shown in Figure l of the drawing, fuelsuch as the primary fuel or propane is introduced as pilot fuel throughconduit 24 into the space formed between support member 13 and igniter26. Primary air is introduced through conduit 20 and the plurality oftangential burner air inlet conduits 21 into the chamber 22 at a pointadjacent the downstream end of conduit 25. The pilot fuel is ignited inchamber 25 and the air which is introduced through tangential inletconduits 21 imparts a helical motion to the gases flowing into theinterior of the porous tube 1S. Primary fuel which can be either in aliquid or a gaseous form is ,introduced into the annular space 18 fromfuel inlet conduit 16. One or more primary fuel inlet conduits can be.utilized if desired. The primary fuel is diffused from annular chamber18 through the porous wall of tube 15 and into the vortex of primary airmoving coaxially through the primary combustion chamber, thus obtainingexcellent mixing. The primary fuel and air mixture is ignited by theburning pilot fuel, after which time the introduction of pilot fuel canbe discontinued. By introducing the fuel uniformly through the wall ofthe primary combustion chamber and introducing the primary air in ahelical motion, as a vortex of air moving coaxially through the burnercombustion chamber, excellent mixing of the fuel and air is obtained anda stable flame results, without the aid of holding means such as a flameholder which would increase the pressure drop through the unit. Thecombustion efficiency obtained in this type of device is thereforesuperior to that obtained in any known type of burner.

A portion of the primary air which is introduced through conduit 20 isdiverted as secondary air and is introduced into the interior of flametube 12 downstream This secondary aix acts as a quench, diluting thecombustion products to ,such an extent that additional burning does notoccur. The addition of secondary air also tends to even off thetemperature of gas phases in the combustion apparatus.

Referring now to Figure 3 of the drawing, parts which are like thosedescribed in connection with Figure l are indicated by like numerals. Inthis modification, charnber 22 of Figure 1 has been omitted and thetangential primary air is introduced directly into the upstream end ofthe primary combustion chamber. Primary air is introduced tangentiallyinto the primary chamber through conduits which prevent the entry ofprimary air into annular chamber 18. In this modification, outer shell11 is composed of two sections, the larger lower section being indicated11. These two sections 11 and 11', are secured together by flanges 31and 32. In this modification, the porous inner tube 15 is shown as ametallic so as to introduce air helically into the annulus between shell11 and burner tube 12 so as to facilitate the formation of a vortex ofair and burning gases in the primary combustion chamber.

In the device shown in Figure 5 of the drawing, primary air isintroduced coaxially into the primary combustion chamber through conduit20. The primary air enters the primary combustion chamber through swirlvanes 41 which impart thereto a spiral motion so as to form a vortex ofair and burning gases in the primary combustion chamber. Ignition isobtained in this modilication in the same manner as in the device ofFigures 1 and 3.

Any fuel can be used which will diffuse through the porous materialforming the wall of the inner tube in the primary combustion chamber'.Conventional jet engine fuels are particularly adapted for use in myimproved burner. J et engine fuels include gasoline, kerosene and otherblends of liquid hydrocarbons. The primary fuel can also be used as thepilot fuel, however, it is preferable to use a more volatile fuel suchas propane as the pilot fuel.

I Wish it to be understood that I do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

That which is claimed is:

1. An improved combustion apparatus comprising an outer shell closed atits upstream end; a constant diameter flame tube comprising a primarycombustion chamber and a secondary combustion chamber, closed at itsupstream end and concentrically positioned within said shell; a constantdiameter porous tube concentrically positioned within the primarycombustion chamber of said llame tube, spaced from the wall of saidflame tube and sealed to said flame tube at the downstream end of saidprimary combustion chamber; a cylindrical igniter chamber positioned inthe closed end of said primary combustion chamber, having a diameterless than that of said porous tube; air inlet means opening into saidouter shell; air inlet conduit means extending tangentially from thechamber formed between said outer shell and said llame tube to theinterior of the igniter chamber; a slm-aller diameter chamber in coaxialcommunication with the upstream end of said igniter chamber; an igniterpositioned in said smaller diameter chamber; a pilot fuel inlet conduitmeans extending into said smaller diameter chamber; and fuel inletconduit means extending into the annular chamber formed between theporous tube and the flame tube.

2. An improved combustion apparatus comprising an outer shell closed atits upstream end; a constant diameter flame tube comprising a primarycombustion chamber and a secondary combustion chamber, closed at itsupstream end and concentrically positioned within said shell, a constantdiameter porous tube concentrically positioned within the primarycombustion chamber of said flame tube, spaced from the wall of saidllame tube and sealed to said llame tube at the downstream end of saidprimary combustion chamber; air inlet means opening into said outershell; air inlet conduit means extending tangentially from the chamberformed between said outer shell and said llame tube to the interior ofthe flame tube; a cylindrical chamber positioned in the closed end ofthe said primary combustion chamber, having a diameter less than that ofsaid porous tube; an igniter positioned in said cylindrical chamber; apilot fuel inlet conduit means extending into said cylindrical chamber;and fuel inlet conduit means extending into the annular chamber formedbetween the porous tube and the flame tube.

3. An improved combustion apparatus comprising an outer shell; aconstant diameter flame tube comprising a primary combustion chamber anda secondary combustion chamber, concentrically positioned within saidshell; a constant diameter porous tube concentrically positioned withinthe primary combustion chamber of said llame tube, spaced from the wallof said llame tube and sealed to said llame tube at the downstream endof said primary combustion chamber; an annular member positioned at theupstream end of said primary combustion chamber so as to form an annulusbetween said outer shell and said llame tube and to seal the upstreamend of said flame tube and the upstream end of said porous tube therebyforming an annular chamber therebetween; a member coaxially disposedwithin said annular member having a cylindrical chamber opening intosaid primary combustion chamber and containing therein an igniter; swirlvanes occupying the annulus between said annular ring and said coaxiallypositioned member and rigidly secured to said members; air inlet meansopening into said outer shell at a point upstream from said swirl vanes;a pilot fuel inlet conduit extending into said chamber in said coaxiallydisposed member; and fuel inlet conduit means extending into the annularchamber formed between the porous tube and the flame tube.

4. An improved com-bustion apparatus comprising an outer shell; aconstant diameter flame tube comprising a primary and a secondarycombustion chamber, concentrically disposed within said shell; aconstant diameter porous tube concentrically disposed within saidprimary combustion chamber, spaced from the wall of said flame tube, andsealed to said llame tube at each end of the primary combustion chamber;means for supplying a Vortex of air to the interior of the llame tubeadjacent its upstream end; means for supplying additional air to theinterior of the flame tube through the flame tube wall at a pointdownstream from the primary cornbustion chamber; means for supplyingfuel to the annular chamber between the llame tube and the porous tube;and means for igniting the fuel and air mixture in the primarycombustion chamber.

References Cited in the file of this patent UNITED STATES PATENTS1,495,164 Coberly May 27, 1924 2,018,582 Theunissen Oct. 22, 19352,561,200 Hess Iuly 17, 1951 2,579,614 Ray Dec. 25, 1951 2,616,257 MockNov. 4, 1952 2,668,592 Piros et al. Feb. 9, 1954 2,841,213 De Piolenc etal. July 1, 1958 Y FOREIGN PATENTS 966,707 France Mar. 8, 1950 691,430Germany May 25, 1940

